Generation of internal stress in the process of solidification of synthetic resin, I : internal stress caused by contraction

When casting resin is cured, the volume contraction takes place from the bridge forming reaction and cooling. When the contraction is caused being free from restraint, the internal stress will not originate, but if geometrically restrained, it will originate. In this report, the relation between the free contraction during the curing process and the internal stress caused by the geometrical restraint is studied on the casting type epoxy resin, and the behavior of the resin related to the cause for the origination of internal stress is considered

Generation of internal stress in the process of solidification of synthetic resin, II : internal stress caused by shearing force

Experiments were planned to ascertain the residual stress occurring in amorphous solid of high polymer. For this, injection molded articles of α-methylstyrene--styrene copolymer and bis-phenol-polycarbonate were used, and dilatometric measurement on the pellet form of the polymers and measurements on heating deformation were adopted. As the results, it is clarified that deformation by residual stress begins to occur at the lower limiting temperature of 2nd order transition region, and considering the activation energy of deformation calculated from rate constants of experimental deformation, the residual stress may be due to the orientational configuration of polymer molecules by molten flaw at the injection procedure

Generation of internal stress in the process of solidification of synthetic resin, III : research of molecular structure change related to internal stress by infrared absorption spectrum

The changes of molecular structures owing to the solidification by casting epoxy resin, and also owing to the solidification by injection molding of polystyrene copolymer were studied with infrared spectrum. Epoxy resin, with cis-cyclohexane-dicarboxylic acid anhydride hardener, firstly seems to be esterified through the opening of epoxy ring and combining with the acid anhydride, and finally to form a net work structure by di-ester and ether formation. This net work formation seems to be related with the generation of the internal stress when restrained. On the other hand, the polarized infrared spectrum of injection molded polystyrene copolymer shows that molecules orientate themselves by rapid cooling of molten flow under high shearing force, as in stretched film, and by heating an injection molded specimen the orientation diminishes and deformation occurs, and this orientation corresponds to the internal stress in the linear polymer